Hy, I'm brasilian and intend to get a VOA at Beijing airport for stay 5 days and after 3 days in HK.

Marcelo, I don't think you can get the VOA at Beijing airport because it's very difficult to get it. Do you fly from Brazil to Beijing and then fly to Hong Kong? If so, I think you can shorten your stay in Beijing to 72 hours so as to avoid visa application process. If you have to stay in Beijing for five days, then you should apply for one entry permit in advance.